Narrative:

I was pilot flying in left seat. We were on our flight planned route flying south bound at 33;000 feet at mach .84 with a 1 mile right offset. I had relieved the captain 5 minutes before the event. The captain had requested climb from ATC from 33;000 feet to 35;000 feet and was told to stand by before departing flight deck. ATC cleared us to 'climb and maintain FL350.' after the first officer confirmed clearance with ATC I set 35;000 in altitude window; confirmed '350' with the first officer and selected the new altitude. The aircraft commenced climb on autopilot and approaching 33;500 feet we received a TCAS traffic advisory followed immediately by TCAS resolution advisory 'descend; descend now.' I disengaged autopilot and leveled airplane momentarily before starting descent.after several seconds and barely 100 feet of descent the conflict resolved as the other aircraft passed behind us at 34;000 feet. After re-engaging autopilot and commencing climb to 35;000 feet we heard the other aircraft query ATC about traffic. The first officer asked ATC to confirm that they cleared us to 35;000 feet which ATC confirmed by saying 'correct.' ATC had no comment regarding traffic conflict. We never acquired the other aircraft visually as we were in IMC. This event occurred because ATC cleared us to climb from 33;000 feet to 35;000 feet with opposing traffic in close proximity at 34;000 feet.

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Original NASA ASRS Text

Title: B777 flight crew reported a traffic advisory for converging traffic while in cruise.

Narrative: I was Pilot Flying in left seat. We were on our flight planned route flying south bound at 33;000 feet at Mach .84 with a 1 mile right offset. I had relieved the Captain 5 minutes before the event. The Captain had requested climb from ATC from 33;000 feet to 35;000 feet and was told to stand by before departing flight deck. ATC cleared us to 'climb and maintain FL350.' After the First Officer confirmed clearance with ATC I set 35;000 in altitude window; confirmed '350' with the First Officer and selected the new altitude. The aircraft commenced climb on autopilot and approaching 33;500 feet we received a TCAS traffic advisory followed immediately by TCAS resolution advisory 'DESCEND; DESCEND NOW.' I disengaged autopilot and leveled airplane momentarily before starting descent.After several seconds and barely 100 feet of descent the conflict resolved as the other aircraft passed behind us at 34;000 feet. After re-engaging autopilot and commencing climb to 35;000 feet we heard the other aircraft query ATC about traffic. The First Officer asked ATC to confirm that they cleared us to 35;000 feet which ATC confirmed by saying 'correct.' ATC had no comment regarding traffic conflict. We never acquired the other aircraft visually as we were in IMC. This event occurred because ATC cleared us to climb from 33;000 feet to 35;000 feet with opposing traffic in close proximity at 34;000 feet.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.